WOW, this control board is cooked!

hi, i just got a fixer upper house, with a fixer upper furnace. what could have caused the board to cook like this? i can easily change the control board, but what's to stop this from happening again? it's a carrier model# 591EXX036000AAAA. there are 3 pictures below
thanks!

WOW, this control board is cooked!

This looks alot like a 120 volt board that was blasted with 240 volts. It could have been a lightning strike nearby as well.

There may be other problems in the house. Turn on an incandescent light, anywhere. It can even be a hand-held drop light. While observing the light, turn on a good-sized 120 volt appliance. This can be the dishwasher, disposal, washing machine, 1500 watt heater, etc. If the light dims or brightens considerably, you likely have a loose neutral somewhere. If this is not repaired, the board (and other stuff) will certainly cook again.

WOW, this control board is cooked!

Unless I miss my assumption
that board belongs to a 80 or 90% furnace (Carrier or Bryant) circa 1980s.

The board interfaces with a wiring harness that is mounted thru the furnace burner vestibule to the blower section.

CAUTION!THIS BOARD IS UNFUSED AND THE CAUSE OF THE SHORT IS NOT IMMEDIATELY APPARENT UPON A VISUAL INSPECTION.
YOU MUST NOT CASUALLY REPLACE THE BOARD UNTIL THE ROOT CAUSE HAS BEEN DETERMINED. tHE END RESULT WOULD BE ANOTHER FRIED BOARD.

tHE WIRING HARNESS MAY BE BAD, OR A VALVE, POSSIBLE EVEN A PIECE OF FOIL INSULATION GROUNDING THE LIMIT TO THE HEAT EXCHANGER.

WOW, this control board is cooked!

Has a small 3 amp 24 volt fuse. If the short is in the 110 volt circuit that won't help. If it got blasted by lightning, everything in that furnace may be shot. Gas valve, motor etc. That is an OLD furnace and you would be better off with a new one IMO. The heat exchangers/cells are probably cracked from old age. A new furnace would be much better value for your $$. Stay away from the cheaper units, some of them are coming from China and other off shore markets. Lennox/Carrier/Rheem are my pics.

WOW, this control board is cooked!

I searched all over the net and could not cross the board by Prt# or furnace model.

So i can't tell if the replacement has a fuse or is even available.

The model design It self is problematic. I have had three encounters with this design and came up losing big each time. I thought I had identified all the possible shorts in the defective parts so I changed them and the wiring harness. Two days later i was giving the HO cred for the repair gone bad towards a new furnace.PLEASE READ THE FOLLOWING. THERE IS A LESSON TO BE LEARNED HERE!!
My worst encounter was when i had become burnt out from running my business.
I signed up with a large company and was was fat and happy not worrying where my next service call was coming from. Then I was dispatched to an HO with a bryant Bryanot like the OP posted. Board was fried. I asked the SM if I could be excused from this call and have the office explain it would be better for them to get a new furnace knowing that the reason for shorting was elusive.

Instead the SM (service manager) advised the customer to change all the parts and wiring. A complete rebuild. The SM was convinced it should mot be a problem and said he'd back me up if it went bad.

The rebuild (just changing every part really) was half the cost of a new furnace.

I did the parts replacement and they fried two day later, ALL of them. The SM did NOT back me up. I quit a week later

WOW, this control board is cooked!

Love the smell of freshly cooked circuit boards. My installers accidentally hooked up a 24 volt humidifier to the 110 volt HUM terminal on a new furnace. Blew the sh*t out of everything. Experience is invaluable. That furnace is shot! Trust us. Feeling a bit fat myself today/ate lots of perogies, turkey and all the goodies yesterday. May repeat the process for Ukrainian Xmas soon.

WOW, this control board is cooked!

Quote:

Originally Posted by yuri

Love the smell of freshly cooked circuit boards. My installers accidentally hooked up a 24 volt humidifier to the 110 volt HUM terminal on a new furnace. Blew the sh*t out of everything. Experience is invaluable. That furnace is shot! Trust us. Feeling a bit fat myself today/ate lots of perogies, turkey and all the goodies yesterday. May repeat the process for Ukrainian Xmas soon.

Cheers

We Celebrate Old Calendar too.

No such thing as a skinny Orthodox American around Christmas and New Year's.

WOW, this control board is cooked!

Hi, again!
Thanks for all the input so far. I believe the replacement board part number is CESO110057-02. I think you guys are probably right about needing to replace the unit but I'm hesitant because it's installed in a place where it's not easily accessible for replacement. The circuit board below appears to have a fuse in the 110V circuit.

Would this give it some protection against burning up again? (Assuming everything else is still operational.)

The previous owner said the last time the system was used, it was for cooling. (She is not a reliable witness though.)

WOW, this control board is cooked!

Unless you have a crystal ball no one will know what happened. Deadshorts can blow a board faster than some fuses will blow. It is usually low voltage to the heat pump but that may be blown by the power surge and 240 volts from its power supply may have blown the furnace board. You may want to get a pro to look it all over. Sorry. Seen LOTS of units damaged by lightning in my 30 yrs and it is a BAD situation.

WOW, this control board is cooked!

Found the same part on a second net search. First one didn't show any thing. Second one showed the part you have with a fuse but under a diff part number. That furnace is going to give you fits. But it's your money.

WOW, this control board is cooked!

Turn the board over and trace the foil runner out from the fuse. I'd bet one side of it goes to either SEC1 or SEC2. If it does, the fuse is on the 24 volt side of the transformer. Very rarely does a board like this have a fuse for the 120 volt side.

You mentioned heat pump. I don't think this board can control a heat pump. Not enough 24 volt terminals. It looks like it can control a single-stage furnace, and a single-stage A/C unit. Some of the other guys here have a lot more experience than I do, and can confirm yes or no.